Variable cam timing systems operate to vary the timing between the camshaft and the crankshaft to optimize engine operation over the entire range of engine operation. Systems such as that described in U.S. Pat. No. 5,117,784 to Schechter et al., vary the timing between the camshaft and crankshaft to achieve improved idle stability, expanded torque curve and the RPM (revolutions per minutes) range of the engine, full control of emission gases and elimination of certain emissions, and elimination of external exhaust gas recirculation components and circuitry.
In order to achieve the above mentioned benefits, the exact position of the camshaft must be known in order to alter fuel control and ignition timing in response to the changing angular position of the camshaft. Known engine control systems operate on the assumption that the camshaft and crankshatft are in a fixed relation to one another. Moreover, known systems require at least one crankshaft revolution after engine crank to identify a first firing cylinder in a predetermined sequence of cylinder firing. Consequently, sequential fuel injection is not initiated until after engine crank when the first firing cylinder is identified.
Accordingly, there exists a need for a system which can detect, during engine operation, the angular position of a camshaft which varies in relation to a crankshaft in order to achieve the above mentioned advantages of a variable position camshaft. In addition there also exists a need to identify the first firing cylinder in a predetermined sequence of cylinder firing in order to initiate sequential fuel injection during engine crank.